Demise of Sea Urchins

We went for a walk on the beach tonight. Our beaches are very shallow so we have huge tides. On the last 3 tides ( different heights) there were thousands of these Heart Sea urchin shells. I'm guessing that the storms recently have dislodged them from the reef and washed up. I have never seen so many before, although there are always some on the beach. We also saw 3 Box Jelly fish washed up - definitely not time to enter the sea yet.